Charging system utilizing excess grid electricity

Abstract

An electric vehicle charging system, for use with an electric grid having live conductors including a charging conductor, and a neutral conductor. The electric grid has a grid usage level and a grid capacity. The charging system includes a plurality of stages that each include a battery charger for charging an electric vehicle battery, a controller, and a charging relay. A current sensing unit inductively measures the current on the charging conductor and provides a sensed current to the controllers. When the grid usage level is low the battery chargers on all stages are active. As the grid usage increases toward peak usage, in response to an increase in the sensed current, the controllers consecutively deactivate the battery chargers at predetermined threshold levels.

What is claimed is: 
     
       1. A charging system, for charging electric vehicle batteries, comprising:
 an electrical grid, having three live conductors and one neutral conductor, one of said live conductors is designated the charging live conductor, the electrical grid having a grid usage level, a peak usage level, and a grid capacity; 
 a current sensing unit having an inductive loop that encircles the charging live conductor such that a sensed current is magnetically induced in the inductive loop in proportion to electricity flowing through the charging live conductor, the current sensing unit also having a bridge rectifier for producing a DC sensed current from the sensed current; 
 a plurality of stages connected to the charging live conductor, each stage having a battery charger, each battery charger adapted to connect to and charge one of the electric vehicle batteries, each stage further having a charging relay having poles and a coil, the poles of the charging relay selectively connecting the battery charger to the live conductor, and a controller connected to the DC sensed current and having an enabling output connected to the coil of said relay, the controller providing an enabling output to energize the coil and disconnect the charger from the live conductor when the DC sensed current reaches a predetermined threshold, wherein the predetermined threshold for each of the stages is different so battery charging occurs on all of the battery chargers when grid usage level is low and that the battery chargers associated with the different stages are consecutively deactivated as the grid usage level increases. 
 
     
     
       2. The charging system as recited in  claim 1 , further comprising a step down transformer having a primary input connected to the charging live conductor and the neutral conductor, and a secondary output selectively connected to the battery chargers through their associated charging relays. 
     
     
       3. The charging system as recited in  claim 2 , wherein the battery chargers are all active when the DC sensed current measures 0 mV, all deactivated at a peak usage sensed current, and are consecutively deactivated in steps equal to the peak usage sensed current divided by the number of stages. 
     
     
       4. The charging system as recited in  claim 2 , wherein the plurality of stages further comprises at least five stages, wherein a peak usage sensed current is measured by the current sensing unit during peak usage of the electrical grid, wherein a step level is the peak usage sensed current divided by the number of stages, wherein the battery charger for one of the stages is deactivated when the sensed current is the step level, the battery charger for another of the stages is deactivated when the sensed current is at two times the step level, the battery charger for another of the stages is deactivated when the sensed current is at three times the step level, the battery charger for another of the stages is deactivated when the sensed current is at four times the step level, and the battery charger for another of the stages is deactivated when the sensed current is at five times the step level. 
     
     
       5. The charging system as recited in  claim 4 , further comprising a tracking computer, connected to the bridge rectifier and to the controllers, for measuring the DC sensed current and tracking activation and deactivation of the controllers alongside the DC sensed current. 
     
     
       6. The charging system as recited in  claim 2 , wherein the current sensing unit and plurality of stages as recited is triplicated, wherein each such current sensing unit and plurality of stages is provided for each of the live conductors such that one of said live conductors serves as the charging live conductor for its associated current sensing unit and plurality of stages. 
     
     
       7. A charging system, for charging electric vehicle batteries using an electrical grid, having three live conductors and one neutral conductor, the electrical grid having a grid usage level, a peak usage level, and a grid capacity, comprising:
 a current sensing unit having an inductive loop that is adapted to encircle one of the live conductors, designated as a charging live conductor, such that a sensed current is magnetically induced in the inductive loop in proportion to electricity flowing through the charging live conductor; 
 a step down transformer having a primary input adapted to connect to the charging live conductor and the neutral conductor, and a secondary output selectively connected to the battery chargers through their associated charging relays; 
 a plurality of stages connected to the secondary output, each stage having a battery charger, each battery charger adapted to connect to and charge one of the electric vehicle batteries, each stage further having a charging relay having poles and a coil, the poles of the charging relay selectively connecting the battery charger to the live conductor, and a controller connected to the sensed current and having an enabling output connected to the coil of said relay, the controller providing an enabling output to energize the coil and disconnect the charger from the live conductor when the sensed current reaches a predetermined threshold, wherein the predetermined threshold for each of the stages is different so battery charging occurs on all of the battery chargers when grid usage level is low and that the battery chargers associated with the different stages are consecutively deactivated as the grid usage level increases. 
 
     
     
       8. The charging system as recited in  claim 7 , wherein the current sensing unit, step down transformer, and plurality of stages as recited is triplicated, wherein each such current sensing unit and plurality of stages is provided for each of the live conductors such that one of said live conductors is adapted to serve as the charging live conductor for its associated current sensing unit and plurality of stages. 
     
     
       9. The charging system as recited in  claim 8 , wherein the current sensing unit also having a bridge rectifier for producing a DC sensed current from the sensed current. 
     
     
       10. The charging system as recited in  claim 9 , wherein the battery chargers are all active when the DC sensed current measures 0 mV, all deactivated at a peak usage sensed current, and are consecutively deactivated in steps equal to the peak usage sensed current divided by the number of stages. 
     
     
       11. The charging system as recited in  claim 9 , wherein the plurality of stages further comprises at least five stages, wherein a peak usage sensed current is measured by the current sensing unit during peak usage of the electrical grid, wherein a step level is the peak usage sensed current divided by the number of stages, wherein the battery charger for one of the stages is deactivated when the sensed current is at the step level, the battery charger for another of the stages is deactivated when the sensed current is at two times the step level, the battery charger for another of the stages is deactivated when the sensed current is at three times the step level, the battery charger for another of the stages is deactivated when the sensed current is at four times the step level, and the battery charger for another of the stages is deactivated when the sensed current is at five times the step level. 
     
     
       12. The charging system as recited in  claim 11 , further comprising a tracking computer, connected to the bridge rectifier and to the controllers, for measuring the DC sensed current and tracking activation and deactivation of the controllers alongside the DC sensed current.